1. Field of the Invention
This invention relates to a decorative enhancement for a rubber article and, more particularly, to a decoratively colored and/or patterned film which may be fused to an ethylene-propylene diene monomer (EPDM) rubber article.
2. Description of the Related Art
EPDM is widely used as a rubbery material in, for example, the automotive industry because it exhibits excellent resistance to ozone deterioration, heat degradation and environmental weathering. In the automotive industry, EPDM rubber has been employed to provide window seals, glass runners, door sponges, weatherstrips, door trim, body side moldings, bumper guards, trunk seals, and the like. In order to provide EPDM rubber with at least some of the above-noted desirable qualities, it is typically formulated with carbon black which results in the finished automotive components being colored black.
Increasingly, automotive manufacturers have been demanding EPDM rubber components in colors other than black. In some instances, the manufacturers desire that the EPDM rubber components be colored to match the body color of a motor vehicle. In other instances, it may be desirable to provide the EPDM rubber components in a contrasting color which decoratively and aesthetically highlights the vehicle. Until the development of the present invention, no commercially useful product which satisfies these demands has been available.
Attempts have been made to reformulate EPDM rubber by replacing the carbon black with white colored fillers or additives such as calcium carbonate or clay and then coloring the rubber with appropriate pigments. Unfortunately, EPDM rubber articles colored in this manner exhibit poor resistance to environmental weathering. Furthermore, the durability and the elasticity of the resulting articles is adversely compromised. Consequently, the rubber articles have been supplemented with various adjuvants such as anti-corrosion inhibitors, ultra-violet absorbers, optical stabilizers and the like. Unfortunately, the environmental weather resistance of these "supplemented" materials is not comparable to EPDM rubber formulated with carbon black. (The articles tend to crack and their color changes with the passage of time.)
In an alternative approach, carbon black-modified EPDM rubber has been painted to provide the desired color. In many instances, the paint forms a relatively hard and inflexible coating which is not compatible with the underlying flexible, rubbery substrate. While some paints demonstrate improved flexibility, they tend to exhibit a low surface strength and are not resistant to scratching and bending.
In still a third approach, carbon black-modified EPDM rubber is coextruded with a thin, colored rubber film which is integral with the EPDM. However, this technique is expensive, time consuming and labor intensive. It is difficult and laborious to not only change the color of the coextruded skin but to accurately match the color of the final product to that which is desired. The color development in these products is generally poor due to the presence of certain ingredients, such as sulfur-based vulcanizers. Moreover, since the skin is coextruded, it cannot be provided with a patterned surface. Also, this process requires the use of a special and dedicated extruder, such as a cross-head type extruder. An example of this approach is disclosed in Japanese Patent Publication No. 61-187.
Consequently, there remains a need for a flexible, durable, colored EPDM rubber article which may be efficiently and economically produced.